Multiscale Modeling of Water Absorption and Mechanical Strength of Polymer Matrix Composite Materials Containing Voids

该奖项支持研究由于与液态水直接接触而导致的含有空隙的复合材料中的水传输，以及相关的材料性能退化。将测量基体聚合物和界面的潜在降解，测试数据将用于校准这种降解的模型。聚合物基复合材料用于暴露于水的结构应用。随着聚合物基复合材料在一些重要结构中得到广泛接受，人们一直担心暴露在潮湿空气中可能会导致性能退化。较少考虑的是复合材料与液态水直接接触的影响。这种暴露在复合材料中存在空隙的情况下，可能允许水以毛细管流动的形式运输。毛细管流动是一种非常快速的运输机制，它将加速扩散到聚合物中，并导致有机聚合物和纤维/基质界面的降解速度加快。美国出口和经济的很大一部分依赖于汽车、飞机和造船行业，这项研究的结果将有利于美国经济和社会。该研究涉及微流体学、材料科学和固体力学等多学科。概述的多尺度方法将涉及来自科学和工程领域代表性不足的群体的学生，并有望以非常积极的方式影响工程教育计划。在聚合物基复合材料中，空隙和孔隙是有害的结构缺陷，不仅会降低材料的强度，还会为基体中的水分扩散之外的吸水和填充提供额外的途径。本项目专门研究水下复合材料的结构缺陷、吸湿性、机械强度和断裂机制之间的干扰等基本问题。具体目标是：(1)利用扫描电子显微镜和微计算机断层扫描技术量化复合材料的结构缺陷，建立可靠的吸水模型并进行微流体测试验证；(2)利用原位扫描电镜（sem）研究了干燥和水时效复合材料的纤维/基体界面强度；(3)建立多尺度细观力学模型，预测宏观复合材料的水老化强度。预测结果将与水老化玻璃/乙烯酯和玻璃/环氧复合材料的实验测量结果进行比较和验证。

This award supports an investigation into water transport in composite materials containing voids due to direct contact with liquid water, and the associated degradation of the performance of the material. The potential degradation of the matrix polymer and the interface will be measured and the test data will be used to calibrate models for such degradation. Polymer matrix composite materials are used in structural applications exposed to water. As polymer matrix composite materials are gaining wide acceptance for several important structures, there has been concern about possible degradation of the performance from exposure to moisture in the form of humid air. Less considered is the influence of direct contact of the composite with liquid water. Such exposure under the presence of voids in the composite may allow water transport in the form of capillary flow. Capillary flow represents a very rapid mechanism of transport which will elevate diffusion into the polymer, and cause increased rate of degradation of the organic polymer and fiber/matrix interface. A substantial fraction of the US export and economy relies on the automotive, aircraft and ship building industries, and results from this research will benefit the US economy and society. This research involves multiple disciplines such as microfluidics, materials science and solid mechanics. The multi-scale approach outlined will involve students from underrepresented groups in science and engineering, and is expected to impact the engineering education program in a very positive manner.Voids and porosity are detrimental structural imperfections in polymer matrix composite materials, not only due to strength reduction, but they provide extra paths for water absorption and filling beyond moisture diffusion in matrix. This project specifically addresses the fundamental problems of the interferences between structural defects, moisture uptake, and mechanical strength and fracture mechanisms of underwater composite materials. Specific objectives are: (1) quantify structural defects in composite materials using scanning electron microscope and micro-computed tomography methods, establish a reliable water uptake model and validate with microfluidics testing; (2) characterize the fiber/matrix interface strength of dry and water-aged composite materials, using in situ scanning electron microscopy on miniature transverse single-fiber and composite tensile specimens; (3) establish a multiscale micromechanical model for prediction the strength of a macroscopic composite exposed to water aging. Predictions will be compared to and validated by the experimental measurements for water-aged glass/vinylester and glass/epoxy composites.